With the development of communication technology, peak rate of a LTE-A (Long Term Evolution Advanced) system is greatly improved compared with a LTE (Long Term Evolution) system, which is required to be 1 Gbps for downlink and 500 Mbps for uplink. Meanwhile, the LTE-A system is required to be compatible well with the LTE system. With an aim of improving the peak rate, the compatibility with the LTE-A system and sufficiently utilizing spectrum resource, a CA (Carrier Aggregation) technology is introduced for the LTE-A system.
In the CA technology, a terminal can work on a plurality of cells at the same time, and a cell can comprise a pair of UL/DL (Uplink/Downlink) CC (Component Carrier) or can only contain the unidirectional UL or DL carrier, instead of the mode only one suit of carrier is included in the LTE system and previous radio communication system. In the CA system, all CCs can either be continuous or discontinuous, and bandwidth of every CC can either be the same or different. To be compatible with the LTE system, the maximum bandwidth of every CC is limited as 20 MHz, and the maximum number of the CC is generally considered as 5 at present.
In addition, the cell of the LTE-A system is classified into:
(1) Primary cell. Only one cell of the cells of UE carrier is defined as Primary cell, PCell for short.
(2) Secondary cell refers to other cells of UE carrier except the Primary cell, SCell for short.
The Primary cell is selected by a base station and is configured for a terminal through RRC (Radio Resource Control) signaling. Different terminals may have different Primary cells. A PUCCH (Physical Uplink Control Channel) is configured on the UL CC of the Primary cell, rather than the UL CC of the Secondary cell.
PHR (Power Headroom Reporting) is a mechanism the UE reporting the difference between the maximum power and the actual sending power of the UE to the base station.
In a LTE Rel-8/9 system, a PH (Power Headroom) is defined aiming to a PUSCH (Physical Uplink Shared Channel) as below:PH=Pcmax,c−PPUSCH Wherein,
Pcmax,c represents the allowable maximum transmission power in the circumstance the terminal meeting a RF indicator.
PPUSCH represents the actual transmission power of the terminal.
In the LTE Rel-8/9 system, the PH is reported through a PHR MAC CE. The PHR MAC CE comprises a MAC subhead and a MAC CE; the structural diagram of the MAC subhead and the MAC CE is respectively shown in FIG. 1 and FIG. 2.
Wherein, meanings of all domains are as follows:
A LCID (Logical Channel Identity) domain: is used to indentify the logical channel of the corresponding load part. For PHR process, the corresponding load part identified by the LCID is PH. The LCID corresponding to the LTE Rel-8/9 PHR is 11010. As shown in Table 1:
TABLE 1UL LCID IdentificationIndexLCID values00000CCCH00001-01010Identity of the logical channel01011-11001Reserved11010Power Headroom Report11011C-RNTI11100Truncated BSR11101Short BSR11110Long BSR11111PaddingWherein,
E domain: extended byte, is used to instruct which one the next byte is, the MAC subhead or the MAC load?
R domain: reserved byte.
PH domain: power headroom domain, is used to bear PH value.
Furthermore, description of the PHR mechanism of the LTE-A system is made as below:
The PH of the LTE-A system is calculated and reported based on the cell. Once the PHR of a cell is triggered, it is required to report the PH information of all configured and activated cells. While real PUSCH/PUCCH transmission is not certainly provided on the activated cell, so a virtual PUCCH/PUSCH format is introduced in the LTE-A system. When PUCCH/PUSCH transmission is not really performed on an activated cell, the PH value on the cell can be calculated with the virtual PUCCH/PUSCH. Detailed format of the virtual PUCCH/PUSCH is specified in physical layer protocol and will not be to introduced hereby.
Different types of PH are defined in the LTE-A system for the Primary cell and the Secondary cell, viz. Type 1 PH and Type 2 PH. The details are as below:
For the PCell, if it is configured on the RRC layer that the PUCCH and PUSCH transmission are not allowed simultaneously, it only needs to report Type 1 PH on the PCell; otherwise, Type 1 PH and Type 2 PH are always reported on the PCell at a time;
For the SCell, only Type 1 PH is reported thereof since the PUCCH is unavailable.
Type1 PH and Type 2 PH are calculated in the following ways:PHPUSCH=Pcmax,c-1−PPUSCH  Type 1PHPUCCH+PUSCH=Pcmax,c-2−PPUSCH−PPUCCH  Type 2
Meanings of all parameters in above formula are shown as below:
PPUSCH represents the transmission power of the PUSCH on the cell;
PPUCCH represents the transmission power of the PUCCH on the PCell;
Pcmax,c-1: represents the configurable maximum transmission power of UE carrier on the cell for calculating the Type 1 PH;
Pcmax,c-2: represents the configurable maximum transmission power of UE carrier on the cell for calculating the Type 2 PH;
It should be noted that, the calculation method of the Pcmax,c-1 and Pcmax,c-1 of the PCell has not been determined.
The format of the PHR MAC CE of the LTE-A system has not been finally determined, but the two principles have been determined as below:
It is required to indicate length of the PHR MAC CE in L domain in the MAC subhead corresponding to the PHR MAC CE;
The PHR MAC CE only comprises the PH on the cell activated by the UE;
Furthermore, the Pcmax,c shall be calculated in the way regulated as below:PCMAX_L−T(PCMAX_L)≦Pcmax,c≦PCMAX_H+T(PCMAX_H)
Wherein, PCMAX_L=MIN{PEMAX_L, PUMAX}
PCMAX_H=MIN{PEMAX_H, PPowerClass}
T(PCMAX_H) is related to the value range of Pcmax,c, Once the value range of the Pcmax,c is determined, the Pcmax,c can be determined;
The PEMAX_L and the PEMAX_H are configured by the RRC layer based on the cell.
The PUMAX represents the maximum transmission power of the UE after considering an A-MPR (Additional Maximum Power Reduction)/MPR (Maximum Power Reduction).
PPowerClass represents the maximum transmission power of the UE without considering the A-MPR/MPR.
In the above parameters, the PEMAX_L and the PEMAX_H are configured by the base station, so it can be known for the base station that the PPowerClass has just one grade at present. Therefore, it can reckon the A-MPR/MPR really used by the UE as long as the base station knows the Pcmax,c on a cell.
In the process realizing the embodiments of the present invention, the is applicant discovers that at least the following problems exist in prior art:
At present, the method for reporting the configurable maximum transmission power of UE carrier in the PHR MAC CE is not described in the protocol.